Cathode spot control



Dec. 20, 1949 R I, L NGIN. 2,491,990

CATHODE SIOT CONTROL Filed Aug. 19, 1948' Insulation INVENTOR RichardL.Longini.

ATTORNEY Patented Dec. 20, 1949 CATHODE SPOT CONTROL Richard L. Longini,Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application August 19,1948, Serial No. 45,010

4 Claims. 1

My invention relates to a vapor-electric device and particularly to anexcitation arrangement for maintaining the cathode spot within apredetermined area on the liquid cathode.

In the operation of metal tank vapor-electric devices, it is necessaryto prevent the attachment of the cathode spot to any portion of themetal container. Heretofore, this has been accomplished mainly by bruteforce methods at great expense and inconvenience. Usually the attachmentof a cathode spot to the metallic container is prevented either bycomplicated shields or by insulating devices interposed between thecathode surface and the metallic container.

I have found that if a conductor is extended upwardly through thesurface of the cathode pool adjacent to the desired position of thecathode spot, and the keep-alive electrode is placed in the vicinity ofthis vertical conductor and a current flows within thevertically-extending conductor (that is, a current flows in theconductor parallel to the keep-alive arc and in the reverse direction),a field will be established about the conductor which will draw thecathode spot into the vicinity of the conductor and prevents itswandering over the surface of the pool so that it might become attachedto the metallic container.

It is an object of my invention to provide an excitation system havinginherent means for restricting the motion of the cathode spot away froma predetermined surface area on the oathode pool.

It is a further object of my invention to provide means for restrictingthe cathode spot to a predetermined portion of a cathode pool.

It is a further object of my invention to provide an improved excitationsystem for a vaporelectric device.

It is a further object of my invention to provide a conductor forestablishing a spot control field in a vapor-electric device.

Other objects and advantages of my invention will be apparent from thefollowing detailed description taken in conjunction with theaccompanying drawing in which the figure is an elevation partially insection of a vapor-electric device containing an excitation systemaccording to my invention.

In the exemplary embodiment of my invention, the vapor-electric devicehas a metallic container I in which is a cathode 2 of vaporizablereconstructing material such as mercury, gallium, cesium, potassium orsodium. Cooperating with this cathode 2 is an anode 3 maintained inspaced insulated relation to the container l by means of a suitableinsulator 4, current being conducted to the anode 3 by means of asuitable lead-in connection 5.

The excitation system according to my invention comprises a make-aliveelectrode in or igniter having a resistance material in contact with aportion of the cathode material 2 and having suitable means such as animpulsing transformer II to produce impulses for initiating a cathodespot on the normally liquid cathode 2.

In order to maintain the cathode spot, a keepalive electrode I 2 ofsuitable material is placed above the cathode surface in the vicinitywhere it is desired to maintain the cathode spot. Also in the vicinitywhere it is desired to maintain the cathode spot is avertically-extending conductor l3 preferably insulated from the cathodematerial by suitable high-temperature insulators I 4.

When a single keep-alive electrode I2 is utilized, it is usuallydesirable to impress a substantially direct-current, keep-alivepotential on the keepalive electrode l0. Also, it is desirable tomaintain a substantially uni-directional current in thevertically-extending conductor i3.

The current connection to the keep-alive electrode l2 may be completelyseparate and distinct from the conductor l3 and such connections may beat times most desirable. When separate supply connections are providedfor the keep-alive electrode [2 and for the conductor l3, the current inthe upward direction in the conductor I3 is adjusted to attract thecathode spot into the vicinity of the conductor I3.

I have found very satisfactory results may be obtained by mounting thekeep-alive electrode I2 on the vertical conductor I 3 and providingmeans for maintaining two substantially inde pendent currents in thevertical conductor I3.

I prefer to maintain these separate currents by providingcurrent-limiting means l8 in the return connection Hi from thekeep-alive electrode I2 and in a return connection H from thevertically-extending conductor I3. Preferably, these current-limitingdevices l8 are impedances connected in series with the various currents.

As a specific example of a supply system, I have shown a transformer 2|]energized from an alternating-current source (not shown), supplyingpotential through a full-wave rectifying device 21, the positiveconnection 22 of which is connected to the vertically-extendingconductor l3. Mounted on this conductor I3 is the keep-alive electrodel2 and also connected to this conductor is a separate return connectionIT.

The currents flowing in the keep-alive circuit ductor I3 is adjusted toattract the spot closely 1 in the vicinity of the conductor I3. Sincethey cathode spot is found to move in a direction reverse to thedirection in which 'a conductor would tend to move, it is believed thatcur'rentsabove that necessary to attract the cathode" spot should beavoided. Also supplied from the source of alternating current is animpulsing transformer 24 for supplying impulses to the make-alive'electrode I0.

When putting a this "system: into operation, the r:impulsingitransformer':24.-will cause the initiation of a cathode spotby passing an impulse through; the make-alive electrode). The keep-aliveelectrode IZ-then picks up to thecathode spot andcauses current to flowthrough the'relay 'which opens the connectionnofthe-*impulsingtransformer 24zand maintains-it :out of action so long as the'keepgaliveelectrode 12 is activated. the event the'keepealivei-arc should go out,the

relay 2 5 their will close,-energizing :the impulsing transformerMandre-initiating the'cathode spot,

Inorderto maintain a cathode. spot-in a desired region adjacent Z t0"thevertically extending con-- ductor -l3-,a current must travel intheupward direction through, the vertically-extending con-- ductor -l 3in excess of the current fiowing'through the keep-alive electrode -l2.-In practice the im-' pedances [8 are adjusted so that the properproportion ofcurrent fiows to maintain the cathode spot, and alsocurrent flows upwardly through,

the vertically-extending conductor 13 to increase thelmagneticlfieldwhich-drawsthecathode spot into the immediate vicinity of theupwardly-em tending conductor cl 3.

Inpractice, I have found that an independent or controlled current=ofthe order of 20 to-30 amperes in-the vertically-extending conductor l3wassample to maintainuthe cathode spotwithin l the-desired region.vvWhen the current became too small therelwas a tendency for the cathodespot to wander out-ofvcontrol distance andfrequently to extend into theregion of the-metallic containeril, while currents-'greaterthan 30amperes were apparently of no material advantage.

While v forpurposeof illustration I have shown a preferred embodiment ofmy invention and described my invention to the best of my present Iunderstanding, I wish it 'to be understood that i I am not limitedtocthe example or explanations herein. given, and it is apparent-"thatmany changes and modifications can be made herein without departing fromthe true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. In a vapor-electric device having a main anode and a pool-typecathode, an exciting system comprising a make-alive electrode, impulsingmeans for applying potential impulses to said make-alive electrode forinitiating an electron emitting spot on' said cathode, a keep-aliveelectrode, circuit means for applying potential to said-keep-aliveelectrode for maintaining said electron emitting spot, a conductorextending upward through said pool adjacent said keepalive electrodeandcircuit means for causing current flow in said conductor upward fromsaid pool for anchoring said-electron emitting spot adjacent saidconductor.

2. In a vapor-electric device having a liquid cathodey'a spot fixingsystem comprising a keepalive electrode positioned adjacent the desiredlocation of the cathode "spot; a conductor extend-"- ing throughth'ecathode =at-the desired location 1 of the cathode'spou-a cathode spotinitiatingelec trode adjacent thedesired location :of the cathode spot,a circuit for deliveringcathode spotinitiat ing potential to saidcathodes'pot initiating electrode, a source of unidirectional currentconnected to said keep-alive'electrodeto' maintain a 1 keep-alive arcbetween said ke'ep alive electrode and said cathode-andcir'cuit meansforproduc-.

ing an (upwardly directed'currentin said conductor in' excess of thecurrent flowing in' said 3. An exciting systeirnt'foria vapor-electricde-"= vice havinga main (anode-and cathode compris---- inganelectrodefor.initiating'an electron emitting condition on said5cathode;a second electrode for maintaining saidelectron emitting condition;connections for impressing a 'potentialfimpulse on said firstelectrod'eya source of substantially constant potential connected tosaid second electrode, a conductor extending :throughthe cathode in thevicinity ofthesecond electrode; circuit I means for causing-a currentto'flow in saidconductor independent ofthe current for maintain-- ingthe emitting-condition ofs'aid-cathodep 4. Ina vapor-electricdevicehaving a vaporizable cathode, a conductor extendingthrough said cathodeat a predetermined-position therein, a keep-alive electrode spaced fromthe surface of the cathode" in the immediate vicinity of-said-coIh'ductor, a source of unidirectional potential and connections formaintaining an exciting-arc be-" tween said cathode and said keep-aliveelectrode and connections for maintaining a current in said conductor,said currenthaving a direction oppo site to and ofgreatermagnitude-thanthe keep-,---

alive arc current.

RICHARD L.-LONGINI.

No references cited.-.

